Family offered his headless corprse for $1 million ... US journalist James Foley, pictured in Aleppo, Syria, who was beheaded by the Islamic State extremist group. Picture: AP / freejamesfoley.org, Nicole TungSource:AAP

Since August, the terrorist group overtaking large swathes of Syria and Iraq, has beheaded two more Americans and a Briton in similar displays of barbarism.

The Islamic fundamentalist group, which has overrun large sections of Iraq and Syria, killing thousands of people in the process, had been financing its military by selling oil produced by the wells in the areas it has captured and by collecting ransom from the governments of its non-American hostages.